Tubular prostheses, such as stents, grafts, and stent-grafts are known for treating abnormalities in various passageways of the human body. In vascular applications, these devices often are used to replace or bypass occluded, diseased or damaged blood vessels such as stenotic or aneurysmal vessels. For example, it is well known to use stent-grafts of a biocompatible graft material supported by a framework, for e.g., one or more stent or stent-like structures, to treat or isolate aneurysms. The framework provides mechanical support and the graft material or liner provides a blood barrier. When implanting a stent-graft, the stent-graft typically is placed so that one end of the stent-graft is situated proximal to or upstream of the diseased portion of the vessel and the other end of the stent-graft is situated distal to or downstream of the diseased portion of the vessel. In this manner, the stent-graft extends through and spans the aneurysmal sac and extends beyond the proximal and distal ends thereof to replace or bypass the dilated wall.
Such tubular prostheses are known to be implanted in either an open surgical procedure or by a minimally invasive endovascular/endoluminal approach. Minimally invasive endovascular stent-grafts for use in treating aneurysms are often preferred over traditional open surgery techniques where the diseased vessel is surgically opened, and a graft is sutured into position bypassing the aneurysm. The endovascular approach generally involves opening a vein or artery with a needle, inserting a guidewire into the vein or artery through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator located inside an associated sheath introducer having a hemostasis valve, removing the dilator and inserting a delivery catheter through the hemostasis valve and sheath introducer into the blood vessel. The delivery catheter with the stent-graft secured therein may then be routed through the vasculature to a treatment site. For example, a stent-graft delivery catheter loaded with a stent-graft can be percutaneously introduced into the vasculature, for e.g., into a femoral artery, and the stent-graft delivered endovascularly to a treatment site, such as across an aneurysm, where it is then deployed.
Some type of visualization of the stent-graft during deployment at the treatment site is necessary, particularly when treating an aneurysm as proper placement of a proximal anchor stent(s) against a seal or landing zone, i.e., a patent portion of the vessel wall proximal of the aneurysm, is critical while at the same time the clinician must avoid inadvertently covering one or more branch vessels that may be near the aneurysm with the graft material of the stent-graft. Generally, one or both ends of the stent-graft will have one or more radiopaque markers sewn thereon, either to the graft material and/or a stent structure, and the clinician will utilize a fluoroscope to observe the deployment by means of X-rays to attempt to assure optimal placement.
Radiopaque markers are typically sewn onto the graft material of a stent-graft and are not sewn or otherwise attached to the stent structure thereof, which is generally either mounted on or within the graft material, because doing so can add undesirable bulk and increase an overall delivery profile of the stent-graft. However radiopaque markers that are sewn onto the graft material of the stent-graft must typically be offset by a few millimeters from a leading or true edge of the graft material due to concerns related to the interaction of the sutures with the edge of the graft material, such as fraying of the edge of the graft material which could result in the radiopaque marker separating therefrom. As a result, the clinician must estimate under fluoroscopy the exact location of the graft material edge when deploying the stent-graft at the treatment site.
An accurate estimation of the leading or true edge of the graft material of the stent-graft may become especially critical in anatomies where short landing or seal zones are present, such as a landing or seal zone near the renal arteries. More particularly, for e.g., when treating an abdominal aortic aneurysm (AAA) that is distal of the renal arteries with a diameter of the renal arteries being typically on the order of 4 mm to 7 mm, the few millimeter offset between the radiopaque marker and the graft material edge may become significant as an inaccurate estimation of the distance therebetween could result in the stent-graft being inadvertently deployed with the leading edge of the graft material thereof partially or entirely covering one or both of the renal arteries. The same is true for placement of a stent-graft for treating a thoracic aortic aneurysm (TAA) that occurs distal of the left subclavian artery (LSA) and the left common carotid (LCC), where improper or inadvertent placement of an edge of the graft material of the stent-graft could interfere with blood flow into these important arteries.
Thus a need exists in the art to provide improved means for visualizing the leading or true edge of the graft material of an endovascular prosthesis, such as a stent-graft, thus allowing for more accurate device placement.